Synchronization detecting circuit and multimode wireless communication apparatus

ABSTRACT

Multimode wireless communication apparatus supports plural wireless communication methods and includes synchronization detecting part. Digital signals output from first A/D part and second A/D part are combined by synchronization detecting part. Synchronization detecting part converts sampling frequencies of respective digital signals and performs other processes when combining digital signals. Synchronization detecting part detects synchronization timing for plural wireless communication methods by plurally performing correlation operation corresponding to respective wireless communication methods for digital signals combined, thereby providing a multimode wireless communication apparatus with its size and power consumption reduced.

THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCTINTERNATIONAL APPLICATION PCT/JP2006/314236.

TECHNICAL FIELD

The present invention relates to a synchronization detecting circuit anda multimode wireless communication apparatus supporting plural wirelesscommunication methods.

BACKGROUND ART

A multimode wireless communication apparatus supporting plural wirelesscommunication methods is disclosed in such as Japanese Patent UnexaminedPublication No. 2003-134569.

As shown in FIG. 21, a conventional multimode wireless communicationapparatus has first cellular radio 1701, second cellular radio 1702, andcontrol part 1703. Usually, a multimode wireless communicationapparatus, even while communicating by either one of the wirelesscommunication methods of first cellular radio 1701 and second cellularradio 1702, needs to always check whether or not communication by theother wireless communication method is possible, and thus has radioswith two different wireless communication methods. This results inincreased power consumption by an amount corresponding to the number ofradios increased. In order to solve the problem, a conventionalmultimode wireless communication apparatus reduces its power consumptionby control part 1703 controlling on and off of the power to firstcellular radio 1701 and second cellular radio 1702.

However, the above-described conventional makeup has plural radios tosupport plural wireless communication methods while sharing a controlpart. Accordingly, with conventional makeup, the circuit size grows asthe number of radios increases, and thus the power consumptionundesirably increases even if the control part controls on and off ofthe power to the radios.

SUMMARY OF THE INVENTION

The synchronization detecting circuit has a first converting partadjusting the sampling frequency of a receiving signal by a firstwireless communication method; a second converting part adjusting thesampling frequency of a receiving signal by a second wirelesscommunication method; an adding part combining digital signals outputfrom the first and second converting parts; a delay part storing thecombined signal from the adding part; a first synchronization detectingpart detecting synchronization timing for the receiving signal by thefirst wireless communication method, from the combined signal stored inthe delay part; and a second synchronization detecting part detectingsynchronization timing for the receiving signal by the second wirelesscommunication method, from the combined signal stored in the delay part.

With the makeup, the delay part can be shared among plural wirelesscommunication systems, thereby reducing the size and power consumptionof the synchronization detecting circuit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating makeup of a multimode wirelesscommunication apparatus according to the first exemplary embodiment ofthe present invention.

FIG. 2 is a block diagram illustrating makeup of a synchronizationdetecting part detecting synchronization timing by cross-correlationoperation, of the multimode wireless communication apparatus accordingto the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating another makeup of thesynchronization detecting part detecting synchronization timing bycross-correlation operation, of the multimode wireless communicationapparatus according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating makeup of a synchronizationdetecting part detecting synchronization timing by auto-correlationoperation, of the multimode wireless communication apparatus accordingto the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating makeup of a synchronizationdetecting part including a bit-shifting rate converting part, of themultimode wireless communication apparatus according to the firstembodiment of the present invention.

FIG. 6 is a block diagram illustrating makeup of a synchronizationdetecting part including a time-division rate converting part, of themultimode wireless communication apparatus according to the firstembodiment of the present invention.

FIG. 7 is a block diagram illustrating makeup of a synchronizationdetecting part including an A/D part-directly-controlling rateconverting part, of the multimode wireless communication apparatusaccording to the first embodiment of the present invention.

FIG. 8 is a block diagram illustrating makeup of a multimode wirelesscommunication apparatus according to the second exemplary embodiment ofthe present invention.

FIG. 9 illustrates makeup of a weight coefficient in the multimodewireless communication apparatus according to the second embodiment ofthe present invention.

FIG. 10 is a block diagram illustrating another makeup of the multimodewireless communication apparatus according to the second embodiment ofthe present invention.

FIG. 11 a block diagram illustrating still another makeup of themultimode wireless communication apparatus according to the secondembodiment of the present invention.

FIG. 12 is a block diagram illustrating makeup of a multimode wirelesscommunication apparatus according to the third exemplary embodiment ofthe present invention.

FIG. 13 illustrates makeup of a preamble signal in the multimodewireless communication apparatus according to the third exemplaryembodiment of the present invention.

FIG. 14 illustrates an output signal supplied to the delay part of themultimode wireless communication apparatus according to the thirdexemplary embodiment of the present invention.

FIG. 15 is a block diagram illustrating another makeup of the multimodewireless communication apparatus according to the third exemplaryembodiment of the present invention.

FIG. 16 illustrates the circumstances of switching of the output to thedelay part of the multimode wireless communication apparatus accordingto the third embodiment of the present invention.

FIG. 17 is a block diagram illustrating a multimode wirelesscommunication apparatus according to the fourth exemplary embodiment ofthe present invention.

FIG. 18 is a flowchart illustrating the operation of the communicationarea judging process of the multimode wireless communication apparatusaccording to the fourth embodiment of the present invention.

FIG. 19 is a block diagram illustrating makeup of a multimode wirelesscommunication apparatus according to the fifth exemplary embodiment ofthe present invention.

FIG. 20 is a flowchart illustrating the operation of the communicationarea judging process of the multimode wireless communication apparatusaccording to the fifth embodiment of the present invention.

FIG. 21 is a block diagram illustrating makeup of a conventionalmultimode wireless terminal

REFERENCE MARKS IN THE DRAWINGS

-   100, 400, 500 Multimode wireless communication apparatus-   110 First RF receiving part-   111 Second RF receiving part-   112 First A/D part-   113 Second A/D part-   121, 321 Synchronization detecting part-   130 First baseband signal processing part-   131 Second baseband signal processing part-   120, 140, 320, 520 Control part-   422, 442 Area judging part-   523 Switch-   530 Baseband signal processing part (Software signal processing    part)-   1211 First-wireless-system-use synchronization detecting part (First    synchronization detecting part)-   1212 Second-wireless-system-use synchronization detecting part    (Second synchronization detecting part)-   1213 Delay part-   1214 Adding part-   1215 First rate converting part (First converting part)-   1216 Second rate converting part (Second converting part)-   1217 First bit-shifting part-   1218 Second bit-shifting part-   1219 First constant delay part-   1220 Second constant delay part-   1221 First averaging part-   1222 Second averaging part-   1230 Weight coefficient adjusting part-   12111, 12121 Weight coefficient-   12112, 12122, 12114, 12124 Multiplying part-   12113, 12123 Adding part-   1501, 1502 Switch-   1701, 1702 Cellular radio-   1703 Control part-   2217 Filter-   3215 First buffer (First converting part)-   3216 Second buffer (Second converting part)-   3217 Third buffer (Replica accumulating part)-   3218 Switch

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, a description is made for some embodiments of the presentinvention, using the related drawings.

First Exemplary Embodiment

FIG. 1 is a block diagram illustrating makeup of multimode wirelesscommunication apparatus 100 according to the first exemplary embodimentof the present invention.

In FIG. 1, multimode wireless communication apparatus 100 includes firstRF receiving part 110, second RF receiving part 111, first A/D part 112,second A/D part 113, synchronization detecting part 121, first basebandsignal processing part 130 as a first signal processing part, and secondbaseband signal processing part 131 as a second signal processing part.

First RF receiving part 110, first A/D part 112, and first basebandsignal processing part 130 process a radio-frequency signal of a firstwireless system in a first wireless communication method; and second RFreceiving part 111, second A/D part 113, second baseband signalprocessing part 131 process a radio-frequency signal of a secondwireless system in a second wireless communication method.

First RF receiving part 110 converts the radio-frequency signal of thefirst wireless system, supplied from the antenna, to anintermediate-frequency analog signal, and then outputs it to first A/Dpart 112. First A/D part 112 converts the analog signal entered to adigital signal, and then outputs it to synchronization detecting part121 and first baseband signal processing part 130.

Second RF receiving part 111 converts the radio-frequency signal of thesecond wireless system, supplied from the antenna, to anintermediate-frequency analog signal, and then outputs it to second A/Dpart 113. Second A/D part 113 converts the analog signal entered to adigital signal, and then outputs it to synchronization detecting part121 and second baseband signal processing part 131.

When synchronization detecting part 121, connected to first A/D part 112and second A/D part 113, is supplied with the digital signal of thefirst wireless system, output from first A/D part 112; and that of thesecond wireless system, output from second A/D part 113, part 121detects timing for both signals.

For example, synchronization detecting part 121 has a function fordetecting timing of removing a guard interval for OFDM (OrthogonalFrequency Division Multiplexing) as a wireless communication method; afunction for detecting timing of a symbol, slot, and frame required fordespreading for CDMA (Code Division Multiple Access). Timings for thetwo wireless communication methods, detected by synchronizationdetecting part 121 are output to first baseband signal processing part130 and second baseband signal processing part 131, respectively.

First baseband signal processing part 130 performs digital signalprocessing such as demodulation for the digital signal supplied fromfirst A/D part 112 on the basis of timing supplied from synchronizationdetecting part 121. Second baseband signal processing part 131 performsdigital signal processing such as demodulation for the digital signalsupplied from second A/D part 113 on the basis of timing supplied fromsynchronization detecting part 121.

In the first embodiment, a description is made for the case where thefirst wireless system uses IEEE 802.11a as the first wirelesscommunication method; and the second wireless system, W-CDMA(Wideband-Code Division Multiple Access) as the second wirelesscommunication method.

Synchronization detecting part 121 detects timing for synchronizationwith a preamble signal for IEEE 802.11a; and with a spread code forW-CDMA. The sampling rate corresponding to the basic sampling frequencyin IEEE 802.11a is 20 M samples/second, and the chip rate correspondingto the basic sampling frequency in W-CDMA is 3.84 M chips/second, andthus sampling frequencies of digital signals fed into synchronizationdetecting part 121 are different between the case where multimodewireless communication apparatus 100 is communicating by IEEE 802.11aand that by W-CDMA.

FIG. 2 is a block diagram illustrating makeup of synchronizationdetecting part 121 detecting synchronization timing by cross-correlationoperation, of multimode wireless communication apparatus 100 accordingto the first embodiment. Synchronization detecting part 121 includesfirst rate converting part 1215 as a first converting part that convertsthe sampling frequency of a receiving signal received by the firstwireless communication method and outputs the digital signal; secondrate converting part 1216 as a second converting part that converts thesampling frequency of a receiving signal received by the second wirelesscommunication method and outputs the digital signal; adding part 1214that combines digital signals with their sampling frequencies convertedfrom receiving signals by first rate converting part 1215 and secondrate converting part 1216; delay part 1213 composed of plural delayelements cascaded (shown by “D” in the figure) that stores and delayscombined signals supplied from adding part 1214;first-wireless-system-use synchronization detecting part 1211 as a firstsynchronization detecting part that detects synchronization timing forthe receiving signal by the first wireless communication method, fromthe combined signal stored and delayed by delay part 1213; andsecond-wireless-system-use synchronization detecting part 1212 as asecond synchronization detecting part that detects synchronizationtiming for the receiving signal by the second wireless communicationmethod, from the combined signal stored and delayed by delay part 1213.Here, delay parts 1213 composed of plural delay elements shown by “D” inthe figure are cascaded with each other. Because there are a largenumber, only some of them are shown for simplicity. In the drawingshereinafter, delay parts 1213 are indicated in the same way.

First-wireless-system-use synchronization detecting part 1211 includesmultiplying part 12112 composed of plural multipliers, and adding part12113. Multiplying part 12112 multiplies weight coefficient 12111(indicated as b₀, b₁, . . . , b_(M−1) (M is a positive integer) in thefigure), by plural digital signals stored in delay part 1213 andadditionally corresponding to weight coefficient 12111, and then outputsthe products to adding part 12113. The sum calculated by adding part12113 is output to first baseband signal processing part 130. Part 1211performs such correlation operation for detecting synchronization timingfor the first wireless system. Here, if the first wireless system usesIEEE 802.11a, weight coefficient 12111 uses the preamble signal in IEEE802.11a.

Second-wireless-system-use synchronization detecting part 1212 includesmultiplying part 12122 composed of plural multipliers, and adding part12123. Multiplying part 12122 multiplies weight coefficient 12121(indicated as a₀, a₁, . . . , a_(M−1), . . . , a_(N−1) (M, N arepositive integers) in the figure), by the plural digital signals storedin delay part 1213 and additionally corresponding to weight coefficient12121, and then outputs these products to adding part 12123. The sumcalculated by adding part 12123 is output to second baseband signalprocessing part 131. Part 1212 performs such correlation operation fordetecting synchronization timing for the second wireless system. Here,if the second wireless system uses W-CDMA, weight coefficient 12121 usesthe spreading code in W-CDMA. Weight coefficients 12111, 12121 can bepreliminarily prepared as tap coefficients or can be read from such as amemory.

In the first exemplary embodiment, the first wireless system uses IEEE802.11a and the second wireless system uses W-CDMA, thus first rateconverting part 1215 and second rate converting part 1216 output asampling frequency being oversampled to the same sampling frequency(i.e. 480 MHz), which is the minimum from among integral multiples ofsample rates or chip rates in both methods, to adding part 1214. Thatis, first rate converting part 1215 oversamples the digital signal inIEEE 802.11a entered by 24 times and outputs it; second rate convertingpart 1216 oversamples the digital signal in W-CDMA entered by 125 timesand outputs it.

Adding part 1214 combines these two digital signals and outputs theresults to delay part 1213. In the makeup as shown in FIG. 2,synchronization detecting part 121 performs correlation operation forall the samples of combined signals. That is, delay part 1213 issupplied with the oversampled digital signals in each wirelesscommunication method. Then, first-wireless-system-use synchronizationdetecting part 1211 uses the preamble signal in IEEE 802.11a oversampledby 24 times with weight coefficient 12111. Meanwhile,second-wireless-system-use synchronization detecting part 1212 uses thespreading code in W-CDMA oversampled by 125 times with weightcoefficient 12121.

At this moment, weight coefficient 12111 remains the same value 24(corresponding to the oversampling number) times continuously, and thusb₀ through b₂₃, b₂₄ through b₄₇, . . . , b_(24×K) through b_(24×(K+1)−1)(K is a positive integer) are all the same, and weight coefficient 12121remains the same value 125 (corresponding to the oversampling number)times continuously, and thus a₀ through a₁₂₄, a₁₂₅ through a₂₄₉, . . . ,a_(125×L) through a_(125×(L+1)−1) (L is a positive integer) are all thesame as well. For example, if the preamble signal in IEEE 802.11aconsists of 320 samples, and the spreading code in W-CDMA consists of256 chips, 7,680 (=320×24) pieces of weight coefficients 12111 andmultiplying parts 12112, and 32,000 (=256×125) pieces of weightcoefficients 12121 and multiplying parts 12122 are required. For delaypart 1213, 32,000 pieces, which is the larger one out of the requirednumbers of weight coefficients and multiplying parts in the two methods,of delay elements are required.

First-wireless-system-use synchronization detecting part 1211 andsecond-wireless-system-use synchronization detecting part 1212 can beconfigured as shown in FIG. 3 as well. FIG. 3 is a block diagramillustrating another makeup of synchronization detecting part 121detecting synchronization timing by cross-correlation operation, ofmultimode wireless communication apparatus 100 according to the firstembodiment.

Next, a description is made for the differences offirst-wireless-system-use synchronization detecting part 1211 andsecond-wireless-system-use synchronization detecting part 1212 in FIG. 3from those in FIG. 2.

In FIG. 2, second-wireless-system-use synchronization detecting part1212 is supplied in parallel with signals without delay output fromadding part 1214 and with signals output from all the delay elements ofdelay part 1213. First-wireless-system-use synchronization detectingpart 1211 is supplied in parallel with signals without delay output fromadding part 1214 and with signals output not from all the plural delayelements of delay part 1213, but from delay elements continuouslycascaded up to a required stage number.

In FIG. 3, on the other hand, second-wireless-system-use synchronizationdetecting part 1212 is supplied directly with the signal without delayoutput from adding part 1214 to delay part 1213, which is the same as inFIG. 2. However, part 1212 is supplied in parallel not with signalsoutput from all the delay elements of delay part 1213, but with signalsoutput from delay elements with discontinuous stage numbers (i.e.skipping a given number of delay elements).

First-wireless-system-use synchronization detecting part 1211 issupplied directly with the signal without delay output from adding part1214 to delay part 1213, which is the same as in FIG. 2. However, part1211 is supplied in parallel not with signals output from all the delayelements of delay part 1213, but with signals output from delay elementswith discontinuous stage numbers (i.e. skipping a given number(generally different from that in second-wireless-system-usesynchronization detecting part 1212) of delay elements out of thosecontinuously cascaded up to a required stage number). Accordingly,weight coefficients 12111 and 12121 are indicated as b₀, b₁, . . . ,b_(M′−1) and a₀, a₁, . . . , a_(N′−1) (M′, N′ are positive integers) inthe figure, respectively.

If synchronization detecting parts 1211 and 1212 in each wireless systemare composed as shown in FIG. 3, synchronization detecting part 121 doesnot perform correlation operation for all the samples, but only forsamples required for detecting synchronization timing. This enablesreducing the numbers of weight coefficients 12111, weight coefficients12121, multiplying parts 12112, and multiplying parts 12122, compared tothe composition shown in FIG. 2. For example, if the preamble signal inIEEE 802.11a consists of 320 samples, and the spreading code in W-CDMAconsists of 256 chips, 32,000 pieces of delay parts 1213 are required inthe same way as in FIG. 2. However, weight coefficients 12111 andmultiplying parts 12112 need to be arranged only by 320 pieces in totalat every 24 pieces of delay elements of delay part 1213. In the sameway, weight coefficients 12121 and multiplying parts 12122 need to bearranged by 256 pieces in total at every 125 pieces of delay elements ofdelay part 1213.

FIGS. 2 and 3 illustrate makeup for performing cross-correlationoperation for detecting synchronization timing. However, makeup forperforming auto-correlation operation as shown in FIG. 4 is alsopossible. FIG. 4 is a block diagram illustrating makeup ofsynchronization detecting part 121 detecting synchronization timing byauto-correlation operation, of multimode wireless communicationapparatus 100 according to the first embodiment. The makeup shown inFIG. 4 is different from that in FIGS. 2 and 3 in that multiplying parts12114, 12124 multiply the digital signals delayed by a certain period byfirst constant delay part 1219 and second constant delay part 1220, bythe digital signals combined by adding part 1214, respectively, toperform correlation (inner product) operation. Here, “a certain period”represents time corresponding to the repetition cycle of a known signalfor each wireless system used for correlation detection in eachsynchronization detecting part, where generally each period is differentfrom the other. Another difference is that first averaging part 1221 andsecond averaging part 1222 are provided that perform averaging processover a given period after correlation (inner product) operation. “Agiven period” during which averaging process is performed representstime corresponding to the repetition cycle of a known signal for eachwireless system used for correlation detection in each synchronizationdetecting part, where generally each period is different from the other.

In FIG. 4, first constant delay part 1219 delays the digital signalsupplied from first rate converting part 1215 by a certain periodpredetermined and then outputs it. Second constant delay part 1220delays the digital signal supplied from second rate converting part 1216by a certain period predetermined and then outputs it. In the firstembodiment, the first wireless system uses IEEE 802.11a and the secondwireless system uses W-CDMA, thus periods delayed by first constantdelay part 1219 and second constant delay part 1220 are predetermined.For example, if the preamble signal in IEEE 802.11a consists of 320samples, and the spreading code in W-CDMA consists of 256 chips, firstconstant delay part 1219 delays by the equivalent of 7,680 samples; andsecond constant delay part 1220, by the equivalent of 32,000 chips.

After multiplying part 12114 multiplies a digital signal delayed by acertain period by first constant delay part 1219, by the digital signaloutput from adding part 1214, first averaging part 1221 performsaveraging process over a certain period, and accordinglyfirst-wireless-system-use synchronization detecting part 1211 performsauto-correlation operation for detecting synchronization timing for thefirst wireless system.

Meanwhile, after multiplying part 12124 multiplies a digital signaldelayed by a certain period by first constant delay part 1220, by thedigital signal output from adding part 1214, second averaging part 1222performs averaging process over a certain period, and accordinglysecond-wireless-system-use synchronization detecting part 1212 performsauto-correlation operation for detecting synchronization timing for thesecond wireless system. Although the makeup as shown in FIG. 4 is lowerin the accuracy of detecting synchronization timing than that in FIGS. 2and 3, the number of multiplying parts can be reduced, therebycontracting the circuit scale of synchronization detecting part 121. InFIG. 4, the output from multiplying part 12114 and multiplying part12124 needs to undergo averaging process over a given section asdescribed above. However, each output may undergo averaging processinternally after it is fed into first baseband signal processing part130 or second baseband signal processing part 131 in FIG. 1, where thesetwo averaging parts 1221 and 1222 may be dispensed with.

FIG. 5 is a block diagram illustrating makeup of synchronizationdetecting part 121 having a bit-shifting rate converting part, ofmultimode wireless communication apparatus 100 according to the firstembodiment. FIG. 5 illustrates the makeup shown in FIG. 2 further havingfirst bit-shifting part 1217 and second bit-shifting part 1218. Parts1217 and 1218 bit-shift the digital signal entered and then output it.For example, if the digital signal in the first wireless system has abit width for 32-bit operation; and the second, 16-bit, secondbit-shifting part 1218 bit-shifts the digital signal by 16 bits, andaccordingly adding part 1214, multiplying part 12112, and multiplyingpart 12122 can operate in 32 bits. Thus, synchronization detecting part121 further has first bit-shifting part 1217 and second bit-shiftingpart 1218 as a bit-shifting part that matches the number of bits foroperation by first-wireless-system-use synchronization detecting part1211 as the first synchronization detecting part andsecond-wireless-system-use synchronization detecting part 1212 as thesecond synchronization detecting part.

This makeup allows synchronization detecting part 121 to detectsynchronization timing accurately even if the digital signals in thefirst and second wireless systems are different in their bit width,where weight coefficients 12111 and 12121 need to be preparedpreliminarily.

As described above, synchronization detecting part 121 of multimodewireless communication apparatus 100 according to the first embodiment,with adding part 1214 shown in FIGS. 2 through 5, combines the digitalsignals in the first and second wireless systems and simultaneouslydetects synchronization timing for the two wireless systems. Ifcombining the digital signals in this way, although the digital signalsin each wireless system become noise components for the other,synchronization timing can be detected because known signals in awireless system, such as the preamble signal and the spreading code forsynchronization detection, generally has a low correlation withreceiving signals in another wireless system.

Under the circumstances, multimode wireless communication apparatus 100,further having an RF receiving part, A/D part, and baseband signalprocessing part of a wireless system different from the first and secondwireless systems, combines the digital signals in three or more wirelesscommunication methods, and accordingly can detect synchronization foreach wireless communication system as well. Alternatively, when awireless system has spare time in a resting state such as incommunication idle time (e.g. standby), synchronization timing may bedetected for the first and second wireless systems by time division.

FIG. 6 is a block diagram illustrating makeup of synchronizationdetecting part 121 having a time-division rate converting part, ofmultimode wireless communication apparatus 100 according to the firstembodiment. FIG. 6 is different from FIG. 2 in that control part 120 isprovided that controls whether or not synchronization timing is to bedetected simultaneously, and switches 1501 and 1502 are further providedthat switch the input from first rate converting part 1215 as the firstconverting part and second rate converting part 1216 as the secondconverting part, to adding part 1214. While the first or second wirelesscommunication method performing communication is in a resting state,controlling switch 1501 and switch 1502 allows detecting synchronizationtiming in the first or second wireless communication method in a restingstate, by time division. In addition, with switches 1501 and 1502controlled by control part 120, the output from first rate convertingpart 1215 and second rate converting part 1216 can be combined andoutput simultaneously, or can be output separately to delay part 1213 bytime division. Thus, outputting by time division enables detectingsynchronization timing further highly accurately because while awireless system is not communicating, a noise component does not occurin the other wireless system.

Furthermore, control part 140 can be provided that controls a samplingfrequency of the digital signals output from first A/D part 112 andsecond part A/D 113 as shown in FIG. 7. FIG. 7 is a block diagramillustrating makeup of synchronization detecting part 121 having an A/Dpart-directly-controlling rate converting part, of multimode wirelesscommunication apparatus 100 according to the first embodiment. FIG. 7 isdifferent from FIG. 2 in that first rate converting part 1215 and secondrate converting part 1216 that are required in synchronization detectingpart 121 shown in FIG. 2 are dispensed with because control part 140directly controls first A/D part 112 and second A/D part 113 to convertthe sampling frequency instead of arranging each rate converting part tocontrol the sampling frequency for the digital signals output from eachA/D part.

In the first exemplary embodiment, the first and second wireless systemsuse IEEE 802.11a and W-CDMA, but not limited to. The sampling rate andchip rate in the two wireless communication methods are not particularlylimited. The rate converting part can use zero insertion, interpolationfilter, linear interpolation, zero-order hold, and others. In FIGS. 5,6, and 7, correlation operation is performed for all the samples in thesame way as in FIG. 2. However, correlation operation can be performedonly for samples required for detecting synchronization timing in thesame way as in FIG. 3, or auto correlation can be performed in the sameway as in FIG. 4.

As described above, multimode wireless communication apparatus 100according to the first embodiment is characterized in that detection ofsynchronization timing performed by first-wireless-system-usesynchronization detecting part 1211 as the first synchronizationdetecting part and second-wireless-system-use synchronization detectingpart 1212 as the second synchronization detecting part is executed onthe basis of the result of correlation operation between a specific codepreliminarily prescribed for the first or second wireless communicationmethod, namely a weight coefficient; and the combined signal of thedigital signals stored in delay part 1213, according to a samplingfrequency. Thus, synchronization timing can be detected even for thecombined signal by both wireless communication methods.

As described above, according to the present invention, a delay part fordetecting synchronization timing can be shared among plural wirelesscommunication systems, thereby contracting the circuit scale of amultimode wireless communication apparatus according to the presentinvention along with reducing the power consumption.

Second Exemplary Embodiment

In the first embodiment, the sampling frequency is set to the same onethat is the minimum from among integral multiples of sampling rates orchip rates in different wireless communication methods. In the secondembodiment, the sampling frequency is set to an integral multiple of thelarger one out of sampling rates or chip rates in the first and secondwireless systems. In the second embodiment, the first wireless system isassumed to use IEEE 802.11a; and the second, W-CDMA as well as in thefirst embodiment. For example, the sampling frequency is assumed to be80 MHz, which is 4 times a sampling rate of 20 M samples/second in IEEE802.11a of the first wireless system with the larger sampling rate.

FIG. 8 is a block diagram illustrating makeup of synchronizationdetecting part 121 of multimode wireless communication apparatus 100according to the second embodiment of the present invention. In FIG. 8,the second embodiment is different from the first in thatsynchronization detecting part 121 has weight coefficient adjusting part1230.

Weight coefficient adjusting part 1230 adjusts the repetition number ofa weight coefficient to adjust a fraction if the sampling frequency isnot an integral multiple of the own sampling rate. Concretely, weightcoefficient 12111 uses a signal oversampled by 4 times the preamblesignal in IEEE 802.11a, and weight coefficient 12121 uses a signaloversampled by approximately 21 (≈80/3.84) times the spreading code inW-CDMA.

That is, each element of weight coefficient 12111 remains the same value4 times continuously in ascending order of element numbers, and thus b₀through b₃, b₄ through b₇, . . . , b_(4×K) through b_(4×(k+1)−1) (K is apositive integer) are the same value. Meanwhile, each element of weightcoefficient 12121 remains the same 20 times or 21 times continuously inascending order of element numbers because the oversampling rate 80/3.84is not an integer. That is, a₀ through a₁₉, a₂₀ through a₄₀, a₄₁ througha₆₁, . . . , a_(X) through a_(X+19), a_(X+20) through a_(X+40), . . . ,a_(Y) through a_(Y+20) (X, Y are positive integers) are the same value.Weight coefficient adjusting part 1230 manages this repetition number sothat the weight coefficient of the second system will be adjusted to thesame value 80/3.84 times continuously on average. For example, if thepreamble signal in IEEE 802.11a consists of 320 samples, and thespreading code in W-CDMA consists of 256 chips, 1,280 (=320×4) pieces ofweight coefficients 12111 and multiplying parts 12112 are required, and5,333 (≈256×80/3.84) pieces of weight coefficients 12121 and multiplyingparts 12122 are required. For delay parts 1213, 5,333 pieces, the largerone, are required.

FIG. 9 illustrates circumstances of repeating of weight coefficient12121 in this case. The number of weight coefficients required for 6chips, for example, is calculated to obtain a round figure as6×80/3.84=125. Meanwhile, 256=6×42+4, and thus from 125 (i.e. theequivalent of 6 chips) and 83 (i.e. the equivalent of remaining 4chips), a calculation can be made as 5,333=125×42+83,125=(20+21+21+21+21+21), and 83=(20+21+21+21). That is, 5,250 (=125×42)pieces out of all the weight coefficients represent 252 (=6×42) chips ofthe spreading codes, and 83 pieces of remaining weight coefficientsrepresent 4 chips of the spreading codes, to represent 256 chips of thespreading codes.

As described above, if the number corresponding to the number of samplesper one chip is 20 or 21, how 20 samples/chip or 21 samples/chip arearranged does not particularly matter. The above description is only anexample and not limited.

First-wireless-system-use synchronization detecting part 1211 andsecond-wireless-system-use synchronization detecting part 1212 can havethe same makeup as in FIG. 3 of the first exemplary embodiment. In thiscase, correlation operation is not performed for all the samples, butfor samples required for detecting synchronization timing in the sameway as in the first embodiment. This allows reducing the numbers ofweight coefficients 12111, weight coefficients 12121, multiplying parts12112, and multiplying parts 12122. For example, if the preamble signalin IEEE 802.11a consists of 320 samples, and the spreading code inW-CDMA consists of 256 chips, 5,333 pieces of delay parts 1213 arerequired in the same way as in FIG. 8. However, weight coefficients12111 and multiplying parts 12112 need to be arranged only by 320 piecesat every 4 pieces of delay parts 1213. In the same way, weightcoefficients 12121 and multiplying parts 12122 need to be arranged onlyby 256 pieces at every 20 or 21 pieces of delay parts 1213.

Furthermore, in the second embodiment, the sampling frequency of secondA/D part 113 (not shown in FIG. 8) and that of second rate convertingpart 1216 are not in a relationship of integral multiple, thusgenerating an unnecessary frequency component in the output from secondrate converting part 1216. Accordingly, as shown in FIG. 10, filter 2217may be inserted between second rate converting part 1216 and adding part1214 to remove an unnecessary frequency component in the output fromsecond rate converting part 1216. FIG. 10 is a block diagramillustrating another makeup of synchronization detecting part 121 ofmultimode wireless communication apparatus 100 according to the secondembodiment. With this makeup, correlation operation is possible with theinfluence of an unnecessary frequency component reduced. In order toremove an unnecessary frequency component, the first and second rateconverting parts can be made of a combination of an interpolation filterand decimation filter.

In this embodiment, the first and second wireless systems use IEEE802.11a and W-CDMA, but not limited to, and makeup of the rateconverting part does not particularly matter. The rate converting partmay be bit-shifting, with a function of bit-shifting the digital signalsas shown in FIG. 5; time-division, with a function of switching theinput to the adding part as shown in FIG. 6; or A/Dpart-directly-controlling, with a function of controlling the samplingfrequency of the digital signals as shown in FIG. 7.

In addition, the sampling frequency is not set to an integral multipleof the largest sampling rate or chip rate, out of those in pluralwireless systems, but may be set to an integral multiple of a samplingrate or chip rate other than the largest one and additionally largerthan the largest sampling rate or chip rate. Alternatively, the largestsampling rate or chip rate may be directly the sampling frequency, wherefirst rate converting part 1215 can be omitted as shown in FIG. 11.

For example, if the preamble signal in IEEE 802.11a consists of 320samples, and the spreading code in W-CDMA consists of 256 chips, 320pieces of weight coefficients 12111 and multiplying parts 12112 arerequired, and 1,333 (≈256×20/3.84) pieces of weight coefficients 12121and multiplying parts 12122 are required. For delay parts 1213, 1,333pieces, the larger one, are required. Weight coefficient 12121 in thiscase is represented in the same way as in FIG. 9. That is, 1,250(=125×10) pieces out of all the weight coefficients represent 240(=24×10) chips of the spreading codes, and 83 pieces of remaining weightcoefficients represent 16 chips of the spreading codes, to represent 256chips of the spreading codes. Here, with such as 125=19×5+5×6, and83=13×5+3×6, each group of the coefficients is represented as 5samples/chip, or 6 samples/chip.

As described above, if the number corresponding to the number of samplesper one chip is 5 or 6, how 5 samples/chip or 6 samples/chip arearranged does not particularly matter. The above description is only anexample and not limited.

As described above, multimode wireless communication apparatus 100according to the second embodiment allows the delay part for detectingsynchronization timing to be shared among plural wireless communicationsystems, thereby contracting the circuit scale of multimode wirelesscommunication apparatus 100 along with reducing the power consumption.

Third Exemplary Embodiment

FIG. 12 is a block diagram illustrating makeup of synchronizationdetecting part 321 of multimode wireless communication apparatus 100according to the third embodiment of the present invention.

Synchronization detecting part 321 in FIG. 12 is different fromsynchronization detecting part 121 in FIG. 2 in that part 321 has firstbuffer 3215 as the first converting part and second buffer 3216 as thesecond converting part, instead of first rate converting part 1215 asthe first converting part and second rate converting part 1216 as thesecond converting part, in FIG. 2, and in that part 321 further hascontrol part 320 directing output to the first and second buffers.

Control part 320 outputs a control signal to first buffer 3215 andsecond buffer 3216 so that digital signals stored in first buffer 3215and second buffer 3216 will be output when detecting synchronizationtiming becomes necessary.

First buffer 3215 outputs the digital signals stored until detecting ofsynchronization timing completes, on the basis of a control signalentered from control part 320, and also stores the digital signalsentered from first A/D part 112 (not shown in FIG. 12). Second buffer3216 outputs the digital signals stored until detecting ofsynchronization timing completes, on the basis of the control signalentered from control part 320, and also stores the digital signalsentered from second A/D part 113 (not shown in FIG. 12).

In the third embodiment, first buffer 3215 and second buffer 3216 areassumed to operate with the same timing due to the common clock. In thesame way as in the first embodiment, the first wireless system isassumed to use IEEE 802.11a; and the second, W-CDMA. In this case, thepreamble signal in IEEE 802.11a is composed of 10 pieces of shortsymbols (SS₀, . . . , SS₉=16×10 samples), the guard interval betweenlong symbols, and two long symbols (LS₀, LS₁=64×2 samples), as shown inFIG. 13. The number of delay parts 1213 required for detectingsynchronization timing is determined by which symbol is used in thepreamble signal for detecting synchronization. Although the wholepreamble signal (320 samples) can be used as in the first or secondembodiment, only one long symbol in the preamble signal can be used,where 64 pieces of delay parts 1213 are required.

Meanwhile, the length (timewise length of a repeated code pattern) ofthe spreading code in W-CDMA is 256, and thus the number of delay parts1213 required for detecting synchronization timing is 256. In the thirdembodiment, the number of delay elements of delay part 1213 required fordetecting synchronization timing is equal to the larger one out of thoserequired in the first and second wireless systems, and thussynchronization detecting part 321 results in being composed of delaypart 1213 including 256 pieces of delay elements; multiplying part 12112including weight coefficient 12111 with 64 elements and 64 pieces ofmultipliers; and multiplying part 12122 including weight coefficient12121 with 256 elements and 256 pieces of multipliers.

That is, in multimode wireless communication apparatus 100 according tothe third embodiment, first buffer 3215 as the first converting part andsecond buffer 3216 as the second converting part are buffers foraccumulating the digital signals, and output the digital signalsaccumulated with their timing adjusted according to the number of delayparts 1213.

The sampling rate in IEEE 802.11a is 20 M samples/second, and the chiprate in W-CDMA is 3.84 M chips/second. Accordingly, if first buffer 3215and second buffer 3216 output the digital signals stored in each bufferat the same timing, the digital signals output from second buffer 3216have a smaller number of samples (chips) not oversampled than thoseoutput from first buffer 3215. Control part 320 thus controls secondbuffer 3216 so that the digital signals output from second buffer 3216will be in a burst way.

For example, control is possible where output is stopped for a certainperiod until 256 chips of the digital signals are stored in secondbuffer 3216 after 256 (same as the number of delay elements of delaypart 1213) chips of the digital signals are continuously output. In thiscase, while 256 chips in W-CDMA are accumulated in second buffer 3216 in0.0000667 (≈256/3.84 M) seconds, 1,333 (≈20 M×256/3.84 M) samples inIEEE 802.11a are input into first buffer 3215.

A description is made for the above process, using the related drawings.FIG. 14 illustrates output signals to the delay part of the multimodewireless communication apparatus according to the third embodiment ofthe present invention, where the horizontal axis indicates elapsed timein the right direction. The upper part of FIG. 14 shows signal xs outputfrom first buffer 3215; and the lower, signal ys output from secondbuffer 3216. As shown in the figure, control is performed wherecontinuous 256 chips of signals ys are output from second buffer 3216 ina burst way at intervals of 1333, 1333, 1334 samples at which x₀, x₁₃₃₃,x₂₆₆₆, x₄₀₀₀, . . . are output from first buffer 3215. In other words,burst output t_(S2) of the output from second buffer 3216 is repeated atevery burst output t_(S1) of the output from first buffer 3215.

In the above-described example, distribution is made as4000=1333+1333+1334, considering that time equivalent to 256 chips is 1cycle for 3 periods because (20 M×256/3.84 M)×3=4000, but the way ofdistribution is not limited to this one.

Meanwhile, when second-wireless-system-use synchronization detectingpart 1212 performs correlation operation for the digital signals outputin a burst way, if synchronization timing falls at the vicinity of bothends (i.e. the beginning and ending) of 256 chips output in a burst way,accurately detecting synchronization timing is difficult. The reason isthat the averaging process performed for correlation over a certainsection is highly likely to be interrupted at the vicinity of both endsof the burst output.

Consequently, as shown in FIG. 15, in order to save a replica of thedigital signal output from second buffer 3216, third buffer 3217 as areplica accumulating part; and switch 3218 for switching the output fromsecond buffer 3216 and third buffer 3217 to adding part 1214 areprovided, and the replica accumulated is output from third buffer 3217before outputting next 256 chips of the digital signals after 256 chipsare output from second buffer 3216 at the current time in a burst way.Such makeup allows accurate detection of synchronization timing.

FIG. 16 illustrates timing at this moment of switching the output todelay part 1213 through adding part 1214, by operating switch 3218 bycontrol part 320, schematically indicating circumstances in whichcontrol part 320 controls switch 3218 to switch the output to addingpart 1214.

In FIG. 16, the horizontal axis indicates elapsed time in the rightdirection. The upper part shows circumstances of output signal 20 fromsecond buffer 3216; and the middle and lower parts, output signals 31and 32 from third buffer 3217, respectively.

First, control part 320 makes second buffer 3216 output digital signal22 and controls switch 3218 so that digital signal 22 will be suppliedto adding part 1214 during time t₀ to t₁. Simultaneously, control part320 controls third buffer 3217 so that digital signal 22 will be storedin third buffer 3217 as well.

Next, control part 320 does not especially perform concrete controlduring time t₁ to t₂, when the digital signal is not output from secondbuffer 3216.

Next, control part 320 makes third buffer 3217 output a replica ofdigital signal 22 at time point t₂, prior to t₃, when t₃ at whichdigital signal 33 is output from second buffer 3216 approaches. Then,during time t₂ to t₃, while the replica of digital signal 22 is beingoutput from third buffer 3217, control part 320 controls switch 3218 sothat the replica of digital signal 22 will be output to adding part1214.

Next, during time t₃ to t₄, while digital signal 33 is being output fromsecond buffer 3216, control part 320 makes second buffer 3216 outputdigital signal 33 and controls switch 3218 so that digital signal 33will be supplied to adding part 1214. Simultaneously, control part 320controls third buffer 3217 so that digital signal 33 will be stored inthird buffer 3217 as well. By repeating this series of operation, thedigital signal output in a burst way at a certain time point,continuously with that output in a burst way immediately before, is tobe supplied to delay part 1213 through adding part 1214.

Here, a replica accumulated in third buffer 3217 does not need to becomposed of all the 256 chips as described above, but of only a dataamount with which a timing signal for synchronization at the vicinity ofboth ends of the digital signal output from second buffer 3216 can bedetected. For example, as shown in the lower part of FIG. 16, controlpart 320 may make output signal 32 from the third buffer output a partof digital signal 22 from third buffer 3217 to adding part 1214, at t₂₁,prior to time point t₃ and additionally after time point t₂. With suchoperation, accurate synchronization timing is available withoutaccumulating all the 256 chips as the replica.

Here, in the above-described two cases, time period during which signaloutput to adding part 1214 continues corresponds to time t₂ to t₄ foroutput signal 31 from the third buffer shown in the middle part of FIG.16; and time t₂₁ to t₄ for output signal 32 from the third buffer shownin the lower part.

Further, the function of third buffer 3217 can be incorporated in secondbuffer 3216 to output the replica of digital signal 22 and digitalsignal 33 continuously.

As described above, multimode wireless communication apparatus 100 ofthe third embodiment further includes third buffer 3217 as the replicaaccumulating part that accumulates the digital signals same as all ofthose accumulated in second buffer 3216 as the second converting part,or part of those from an end, and is characterized in that the replicaaccumulating part completes outputting of digital signals to adding part1214 previously accumulated before the second converting part startsoutputting the digital signals. Thus, delay part 1213 can be sharedamong plural wireless communication systems, thereby reducing the sizeand power consumption of multimode wireless communication apparatus 100.Multimode wireless communication apparatus 100 according to the thirdembodiment can detect synchronization timing at a low sampling frequencyonly when necessary and with both ends of the sampled receiving signalcorrected, thereby allowing highly accurate detection of synchronizationtiming.

In this embodiment, the first and second wireless systems are assumed touse IEEE 802.11a and W-CDMA, but not limited to.

As described above, according to the present invention, the delay partfor detecting synchronization timing can be shared among plural wirelesscommunication systems, thereby reducing the circuit scale of multimodewireless communication apparatus 100.

Multimode wireless communication apparatus 100 according to the thirdembodiment is characterized in that the first and second convertingparts are buffers for accumulating receiving signals and output thedigital signals accumulated with their timing adjusted according to thenumber of delay parts 1213. Delay part 1213 thus can be shared amongplural wireless communication systems, and synchronization timing can bedetected at the low sampling frequency only when necessary.Consequently, multimode wireless communication apparatus 100 in thethird embodiment can detect synchronization timing at a lower samplingfrequency than that in the first embodiment, thereby further reducingthe power consumption.

Fourth Exemplary Embodiment

FIG. 17 is a block diagram illustrating makeup of multimode wirelesscommunication apparatus 400 according to the fourth exemplary embodimentof the present invention. As shown in FIG. 17, multimode wirelesscommunication apparatus 400 of the fourth embodiment further includesarea judging part 422 in addition to the makeup of multimode wirelesscommunication apparatus 100 of the first embodiment.

Area judging part 422 judges that the communication apparatus is withina communication service area if the peak value of the results ofcorrelation operation entered from synchronization detecting part 121exceeds a given threshold; and out of the communication service area,otherwise. Further, area judging part 422 outputs a signal for turningon/off of the power, to first baseband signal processing part 130 andsecond baseband signal processing part 131 on the basis of the judgementresult for the first and second wireless systems.

FIG. 18 is a flowchart illustrating the operation of communication areajudging process of multimode wireless communication apparatus 400according to the fourth embodiment. The operation of multimode wirelesscommunication apparatus 400 shown in FIG. 17 is described using theflowchart of FIG. 18.

First, area judging part 422 judges whether or not the communicationapparatus is within an area communicatable by the first wireless systemon the basis of the result of correlation operation by synchronizationdetecting part 1211 (step S401). If judged as out of the communicationservice area (“No” in S401), namely if the first wireless system is notavailable for communication, area judging part 422 turns off the powerto first baseband signal processing part 130 (step S407), and then theprocess proceeds to step S403.

Meanwhile, if judged as within the communication service area (“Yes” inS401), namely if the first wireless system is available forcommunication, area judging part 422 checks the state of the power tofirst baseband signal processing part 130 (step S402). Then, if thepower to first baseband signal processing part 130 is on (“Yes” inS402), the process proceeds to step S403. If off (“No” in S402),however, area judging part 422 turns on the power to first basebandsignal processing part 130 (step S405), and then the process proceeds tostep S403.

Next, area judging part 422 judges whether or not the communicationapparatus is within the area communicatable by the second wirelesssystem on the basis of the result of correlation operation bysynchronization detecting part 1212 (step S403). If judged as out of thecommunication service area (“No” in S403), namely if the second wirelesssystem is not available for communication, area judging part 422 turnsoff the power to second baseband signal processing part 131 (step S408),and then completes the communication area judging process.

Meanwhile, if judged as within the communication service area (“Yes” inS403), namely if the second wireless system is available forcommunication, area judging part 422 checks the state of the power tosecond baseband signal processing part 131 (step S404). Then, if thepower to second baseband signal processing part 131 is on (“Yes” inS404), part 422 completes the communication area judging process. If off(“No” in S404), however, part 422 turns on the power to second basebandsignal processing part 131 (step S406) and then completes thecommunication area judging process.

Here, the communication area judging process does not need to beperformed for the first wireless system first, but can be performed forthe second one first. In addition, the process does not need to usethreshold judgement for the peak among correlation operation results,but may use any means as long as it uses correlation operation results,such as the difference between the peak among correlation operationresults and the noise level.

As described above, multimode wireless communication apparatus 400according to the embodiment includes first baseband signal processingpart 130 as the first signal processing part that demodulates thedigital signal from first A/D part 112, in accordance withsynchronization timing supplied from first-wireless-system-usesynchronization detecting part 1211 as the first synchronizationdetecting part; second baseband signal processing part 131 as a secondsignal processing part that demodulates the digital signal from secondA/D part 113, in accordance with synchronization timing supplied fromsecond-wireless-system-use synchronization detecting part 1212 as thesecond synchronization detecting part; and area judging part 422, wherepart 422 judges the possibility of communication by a wireless systemusing correlation operation results supplied from synchronizationdetecting part 121. If area judging part 422 judges as wirelesscommunication impossible, part 422 turns off the power to the first orsecond signal processing part that demodulates the digital signal in thewireless communication method that has been judged as wirelesscommunication being impossible. In this way, only the baseband signalprocessing part supporting the wireless system communicatable isoperated, and thus multimode wireless communication apparatus 400according to the embodiment can further reduce the power consumption.

Fifth Exemplary Embodiment

FIG. 19 is a block diagram illustrating makeup of multimode wirelesscommunication apparatus 500 according to the fifth embodiment of thepresent invention. Multimode wireless communication apparatus 500 inFIG. 19 is different from multimode wireless communication apparatus 400according to the fourth embodiment, shown in FIG. 17 in that apparatus500 includes baseband signal processing part 530 as a software signalprocessing part, instead of first baseband signal processing part 130and second baseband signal processing part 131, and further includesswitch 523 and control part 520. Another difference from the fourthembodiment is that judgement results from area judging part 442 aresupplied to control part 520.

Baseband signal processing part 530 implements a general-purpose signalprocess by hardware and a function specific to each communicationmethod, by software. In the fifth embodiment, baseband signal processingpart 530 can support IEEE 802.11a and W-CDMA, where control part 520switches between the function of first baseband signal processing part130 of multimode wireless communication apparatus 100 according to thefirst embodiment shown in FIG. 1, and that of second baseband signalprocessing part 131.

Switch 523 switches the input of digital signals from first A/D part 112and second A/D part 113, and is controlled by control part 520. Morespecifically, control part 520 sets switch 523 so that an output signalsupplied from first A/D part 112 will be input to baseband signalprocessing part 530, if baseband signal processing part 530 has thefunction of first baseband signal processing part 130; and part 520switches so that an output signal supplied from second A/D part 113 willbe input to baseband signal processing part 530, if baseband signalprocessing part 530 has the function of second baseband signalprocessing part 131.

Control part 520 controls switch 523 and baseband signal processing part530 on the basis of the judgement result by area judging part 442, andif the result indicates that communication is possible only by the firstwireless system, part 520 directs baseband signal processing part 530 sothat part 530 will support the first wireless system.

If the judgement result indicates that communication is possible only bythe second wireless system, control part 520 directs baseband signalprocessing part 530 so that baseband signal processing part 530 willsupport the second wireless system. If the judgement result indicatesthat communication is possible or impossible by both wireless systems,control part 520 determines so that baseband signal processing part 530will support the first or second wireless system, according topredetermined priority.

If communication is possible or impossible by both wireless systems,judgement can be made by comparing the results of correlation operationperformed by first-wireless-system-use synchronization detecting part1211 and that by second-wireless-system-use synchronization detectingpart 1212. Such methods include comparing the peak values between therespective results of correlation operation, and comparing thedifferences between the peaks among correlation operation results andthe noise level.

If communication is impossible by both wireless systems, decision can bemade on conditions such as larger cover area or higher receptionsensitivity out of the first and second wireless systems. Ifcommunication is possible by both wireless systems, less expensivecommunication charge or lower power consumption can be such a condition.Alternatively, a user of the multimode wireless communication apparatusmay select a wireless system.

FIG. 20 is a flowchart illustrating the operation of the communicationarea judging process of the multimode wireless communication apparatusaccording to the embodiment. The operation of multimode wirelesscommunication apparatus 500 shown in FIG. 19 is described using theflowchart of FIG. 20.

First, area judging part 442 judges whether or not the communicationapparatus is within an area communicatable by the first wireless systemon the basis of the result of correlation operation by synchronizationdetecting part 1211 (step S501).

If judged as out of a communication service area (“No” in S501), areajudging part 442 judges whether or not the communication apparatus iswithin an area communicatable by the second wireless system on the basisof the result of correlation operation by synchronization detecting part1212 (step S505). If judged as out of the communication service area(“No” in S505), the process proceeds to step S503. Meanwhile, if judgedas within the communication service area (“Yes” in S505), namely if onlythe second wireless system is available for communication, basebandsignal processing part 530 begins to support the second wireless system(step S506), and then completes the communication area judging process.

Meanwhile, in step S501, if judged as within the communication servicearea through the first wireless system (“Yes” in S501), judgement is aswell made whether or not the communication apparatus is within the areacommunicatable by the second wireless system on the basis of the resultof correlation operation by synchronization detecting part 1212 (stepS502). If judged as within the communication service area (“Yes” inS502), the process proceeds to step S503. Meanwhile, if judged as out ofthe communication service area (“No” in S502), namely if only the firstwireless system is within the communicatable area, baseband signalprocessing part 530 begins to support the first wireless system (stepS504), and then completes the communication area judging process.

The current state is that communication is possible or impossible byboth the first and second wireless systems, and thus control part 520determines if the first wireless system is to be supported, according togiven priority (step S503). If determined so (“Yes” in S503), basebandsignal processing part 530 begins to support the first wireless system(step S504), and then completes the communication area judging process.Meanwhile, if determined otherwise (“No” in S503), baseband signalprocessing part 530 begins to support the second wireless system (stepS506), and then completes the communication area judging process.

Here, the communication area judging process does not need to beperformed for the first wireless system first, but can be performed forthe second one first.

If the area determining process of the fifth embodiment is applied tomultimode wireless communication apparatus 400 in FIG. 17 of the fourthembodiment, the following control is possible. That is, in S506, thepower to first baseband signal processing part 130 in FIG. 17 is turnedoff instead of assigning baseband signal processing part 530 to supportthe second wireless system in FIG. 19; and in S504 as well, the power tosecond baseband signal processing part 131 is turned off instead ofassigning baseband signal processing part 530 to support the firstwireless system.

Synchronization detecting part 121 can detect synchronization timing forthree or more wireless systems, and thus as a result thatsynchronization detecting part 121 performs correlation operation usinga weight coefficient used for detecting synchronization timing for awireless system other than the first or second wireless system, areajudging part 442 can judge the communication service area for pluralwireless systems. Making baseband signal processing part 530 supportthree or more wireless systems enables multimode wireless communicationapparatus 500 according to the present invention to support three ormore wireless systems.

As described above, multimode wireless communication apparatus 500according to the embodiment includes baseband signal processing part 530as a software signal processing part that switches operation includingeither one of a first signal process that demodulates the digital signalfrom first A/D part 112 in accordance with synchronization timing fromfirst-wireless-system-used synchronization detecting part 1211 as thefirst synchronization detecting part; and a second signal process thatdemodulates the digital signal from second A/D part 113 in accordancewith synchronization timing from second-wireless-system-usesynchronization detecting part 1212 as the second synchronizationdetecting part, on a given condition. The software signal processingpart is characterized in that it performs either one of the first andsecond signal processes corresponding to a wireless communication systemthat has been judged as wireless communication being possible by areajudging part 442. Other characteristics include that a signal process bythe software signal processing part is determined to either one of thefirst and second signal processes by comparing the results ofcorrelation operation by the first and second synchronization detectingparts.

Multimode wireless communication apparatus 100 according to theembodiment can thus share the delay part among plural wirelesscommunication systems and does not have plural baseband signalprocessing parts 530, thereby reducing the circuit scale and powerconsumption.

INDUSTRIAL APPLICABILITY

As described above, the present invention facilitates downsizing andreducing the power consumption of an apparatus, and thus is useful for asynchronization detecting circuit and a multimode wireless communicationapparatus.

1. A synchronization detecting circuit comprising: a first convertingpart that converts a sampling frequency of a receiving signal receivedby a first wireless communication method and outputs a first digitalsignal; a second converting part that converts a sampling frequency of areceiving signal received by a second wireless communication method andoutputs a second digital signal; an adding part that combines the firstdigital signal with the second digital signal; a delay part that delaysthe combined signal output from the adding part; a first synchronizationdetecting part that detects synchronization timing for the receivingsignal by the first wireless communication method from the combinedsignal delayed; and a second synchronization detecting part that detectssynchronization timing for the receiving signal by the second wirelesscommunication method from the combined signal delayed.
 2. Thesynchronization detecting circuit of claim 1, further comprising: aswitch that switches input from the first converting part and the secondconverting part to the adding part, wherein synchronization timing isdetected by time-division method by controlling the switch whencommunication is not being performed by the first or second wirelesscommunication method.
 3. The synchronization detecting circuit of claim1, wherein the first and the second converting parts accumulate thereceiving signal by first and second wireless communication methods,respectively, and adjust timing for the first and second digital signalsconverted according to the number of the delay parts and output thefirst and second digital signals, respectively.
 4. The synchronizationdetecting circuit of claim 3, further comprising: a replica accumulatingpart that accumulates a digital signal identical to the whole seconddigital signal accumulated by the second converting part, or to part ofthat from an end, wherein the replica accumulating part completesoutputting of the second digital signal previously accumulated to theadding part immediately before outputting of the second digital signalfrom the second converting part to the adding part starts.
 5. Thesynchronization detecting circuit of claim 1, wherein detectingsynchronization timing by the first and second synchronization detectingparts is based on a result of correlation operation between a specificcoefficient preliminarily prescribed by the first or second wirelesscommunication method, and the combined signal of the digital signalsdelayed, according to the sampling frequency.
 6. The synchronizationdetecting circuit of claim 1, further comprising: a bit-shifting partthat matches the number of bits for operation by the first and secondsynchronization detecting parts.
 7. A multimode wireless communicationapparatus comprising: the synchronization detecting circuit of claim 1.8. A multimode wireless communication apparatus comprising: thesynchronization detecting circuit of claim 5; and an area judging partthat judges possibility of wireless communication according to theresult of correlation operation.
 9. The multimode wireless communicationapparatus of claim 8, further comprising: a first signal processing partthat demodulates the first digital signal in accordance withsynchronization timing from the first synchronization detecting part;and a second signal processing part that demodulates the second digitalsignal in accordance with synchronization timing from the secondsynchronization detecting part, wherein, when the area judging partjudges as wireless communication being impossible, power to the first orsecond signal processing part that demodulates a digital signal in awireless communication method judged as wireless communication beingimpossible is turned off.
 10. The multimode wireless communicationapparatus of claim 8, further comprising: a software signal processingpart that switches operation including either one of: a first signalprocess that demodulates the first digital signal in accordance withsynchronization timing from the first synchronization detecting part;and a second signal process that demodulates the second digital signalin accordance with synchronization timing from the secondsynchronization detecting part, on a given condition, wherein thesoftware signal processing part performs either one of the first andsecond signal processes corresponding to a wireless communication systemjudged as wireless communication being possible by the area judgingpart.
 11. The multimode wireless communication apparatus of claim 10,wherein the signal process by the software signal processing part isdetermined to either one of the first and second signal processes, bycomparing a result of correlation operation of the first and secondsynchronization detecting parts.